DE 28 52 057 discloses a cooled gas turbine, in which the cooling air extracted from the compressor is cooled by means of water injection. To this end the gas turbine has a water pipe which terminates in a water spray chamber. The water spray chamber is radially limited by the rotor on one side and by a fixed wall embracing the rotor on the other side. The water sprayed in atomizes in the water spray chamber into small water droplets, which evaporate there only partially. The rotor is cooled in this way. The cooled cooling air is then routed further to the blades of the front turbine stages. The water droplets remaining in the cooling air now evaporate in the blade, in order to keep the temperature of the cooling air low there.
The water droplets can lead to corrosion and wear on their path along the rotor and in the blade.
Moreover the water droplets in part wet the inner sides of the blade walls. The result is that particularly well cooled regions of the blade walls adjoin unwetted and thus less cooled regions. A significant temperature gradient can arise in the wall material at the transitions between these regions, which then results in thermal stresses. This can reduce the lifetime of the blade.
Furthermore, EP 0 447 886 A1 discloses an axial-flow cooled gas turbine with a compressor. The gas turbine has a turbine stage, the vanes and blades of which, arranged one behind the other in rings, are cooled by means of cooling air. To this end compressed air is extracted as a coolant downstream of the blade row of the last compressor stage and is routed along the rotor, which is in this case cooled by convection. The cooling air is then fed to the turbine stage downstream of the rotor in the direction of coolant flow.